Just remember it is easier to take out air out than it is to put it in!
For road tyres I used to just put in the maximum pressure written on the sidewall.
Then after the drive take them back down to the maximum pressure on the front and 4psi less on the rear. Which was usually 44psi front 40psi rear warm.
Then I would play with them after each session depending on what the car was doing.
With semi-slicks I found that lower pressures worked better, I presume because the stiffer sidewalls meant that you weren't using the air to "stiffen up" the tyres.
Anyway, it worked for me, but I am not Sydneykid... *dreads his reply*